Abstract

The development of anti-cancer therapeutics that target non-apoptotic pathways has received increasing attention from the scientific community in recent years. The prevalence of chemoresistance and the characterization of defective apoptotic pathways in cancer has promoted interest in the expansion of current therapeutic regimens to include drugs that induce non-apoptotic cell death. From a phenotypic screen we have identified a small molecule named C6 that induces caspase-independent, non-apoptotic cell death in chemoresistant patient-derived breast cancer cells. Additionally, C6 is also selectively cytotoxic against cancer cells compared to normal mammary epithelial cells. In an effort to characterize this small molecule's mechanism of action and identify relevant biological pathways that might be used as therapeutic drug targets, we have utilized a photoaffinity pull-down strategy to identify biological binding partners of C6. Our photoaffinity pull-down studies have revealed Mitsugumin 23 (MG23), an endoplasmic reticulum-bound transmembrane protein capable of ion channel formation, as a binding partner for C6. Additionally, we have identified a metabolic component of C6-induced cell death through the use of mitochondrial respiration measurements, metabolomic analyses, and mitochondrial transmission electron microscopy (TEM) imaging. Metabolic studies have identified mitochondrial respiration defects, excess lactic acid production, and gross changes in mitochondrial morphology as a result of C6 treatment. Collectively, our findings suggest a role for ionic imbalance and subsequent metabolic disruption in this form of caspase-independent cell death. Our ongoing work is focused on further mechanistic characterization of this non-apoptotic pathway as a potential target for breast cancer drug development.